Calibration of the accelerometer sensor of a remote controller

ABSTRACT

A method and a video game system are disclosed for maintaining the readings of the accelerometer sensor of the remote controller used in conjunction with the video game system consistent over different controllers and different styles of play. The video game system looks at a predetermined time period, when the largest difference in the acceleration vectors for each frame is within a small limit, indicating that the player is holding the controller relatively idle. Then, the video game system averages the acceleration vectors over this time period, and the inverse of the magnitude of this average is used as a normalization constant.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Application 61/175,081, filed May 4, 2009, the entire contents of which is incorporated herein by reference.

TECHNICAL FIELD

The technology herein relates to a method and a system for calibrating the operation of the acceleration sensor of a controller used in conjunction with a game system.

BACKGROUND AND SUMMARY

User inputs to computer systems may be supplied in various ways. For example, when the computer system is a video game console, inputs are typically supplied using cross-switches, joysticks, buttons and the like provided on a controller. A cross-switch or a joystick may be used to control movement of a video game object in various directions and various buttons may be used to control character actions such as jumping, using a weapon and the like.

The controller described in this patent application additionally or alternatively includes an accelerometer arrangement that generates inputs to a video game console or other computer system based on certain movements and/or orientations of the controller. Such a controller can provide a more intuitive user interface in which, for example, movement of a video game object can be controlled by moving the controller in a particular manner. By way of illustration, a player may increase or decrease the altitude of a plane in a video game by tilting the controller up or down. The accelerometer arrangement can be used to provide gaming experiences that cannot be provided easily (if at all) using a controller having cross-switches, joysticks, buttons, etc.

Different accelerometers can sometimes provide different readings when subjected to the same motion (acceleration). These different readings can result from, for example, differences in the electrical or mechanical components of the accelerometers. Thus, there can be differences in the accelerometer outputs of accelerometers respectively provided in first and second controllers even when these controllers are moved or held in the same manner.

Moreover, in the case of a multi-axis accelerometer, the sensitivity of each axis to the same acceleration may be different. For example, an accelerometer output generated when a user holds a controller so that the gravity is aligned with a first axis (e.g., the Y-axis) may be different from an accelerometer output generated when the controller is rotated so that the gravity is aligned with a second axis (e.g., the X-axis). This means that the way the user plays a game, for example, if he/she sits down or moves the orientation of the wrist, can affect the measured acceleration values.

The systems and methods described herein provide a normalization constant for normalizing accelerometer outputs so that they are consistent between different accelerometers, and even for different axes of the same accelerometer. This provides a gaming environment in which the motion of the controller can be translated into motion of player characters on the video screen in a consistent and natural way.

By way of example and without limitation, the video game system looks at a predetermined time period, when the largest difference in the acceleration vectors for each frame is within a small limit, indicating that the player is holding the controller relatively idle. Then, the video game system averages the acceleration vectors over this time period, and the inverse of the magnitude of this average is used as a normalization constant.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages will be better and more completely understood by referring to the following detailed description of exemplary non-limiting illustrative implementations in conjunction with the drawings of which:

FIG. 1 is a diagram of an example game system 10.

FIG. 2 is a block diagram of example game console 100 shown in FIG. 1.

FIGS. 3A and 3B are perspective views of a top and a bottom of example controller 107 shown in FIG. 1.

FIG. 4 is a front view of example controller 107 shown in FIG. 1.

FIG. 5A is a block diagram of example controller 107 shown in FIG. 1.

FIG. 5B is used in an explanation of the pointing direction of example controller 107.

FIGS. 6 and 7 show exemplary illustrative non-limiting software flowcharts for the normalization and re-calibration processes.

DETAILED DESCRIPTION

FIG. 1 shows a non-limiting example game system 10 including a game console 100, a television 102 and a controller 107.

Game console 100 executes a game program or other application stored on optical disc 104 inserted into slot 105 formed in housing 110 thereof. The result of the execution of the game program or other application is displayed on display screen 101 of television 102 to which game console 100 is connected by cable 106. Audio associated with the game program or other application is output via speakers 109 of television 102. While an optical disk is shown in FIG. 1, the game program or other application may alternatively or additionally be stored on other storage media such as semiconductor memories, magneto-optical memories, magnetic memories and the like.

Controller 107 wirelessly transmits data such as game control data to the game console 100. The game control data may be generated using an operation section of controller 107 having, for example, a plurality of operation buttons, a key, a stick and the like. Controller 107 may also wirelessly receive data transmitted from game console 100. Any one of various wireless protocols such as Bluetooth (registered trademark) may be used for the wireless transmissions between controller 107 and game console 100.

As discussed below, controller 107 also includes an imaging information calculation section for capturing and processing images from light-emitting devices 108 a and 108 b. Although markers 108 a and 108 b are shown in FIG. 1 as being above television 100, they may also be positioned below television 100. In one implementation, a center point between light-emitting devices 108 a and 108 b is substantially aligned with a vertical center-line of display screen 101. The images from light-emitting devices 108 a and 108 b can be used to determine a direction in which controller 107 is pointing as well as a distance of controller 107 from display screen 101. By way of example without limitation, light-emitting devices 108 a and 108 b may be implemented as two LED modules (hereinafter, referred to as “markers”) provided in the vicinity of the display screen of television 102. The markers each output infrared light and the imaging information calculation section of controller 107 detects the light output from the LED modules to determine a direction in which controller 107 is pointing and a distance of controller 107 from display 101 as mentioned above.

With reference to the block diagram of FIG. 2, game console 100 includes a RISC central processing unit (CPU) 204 for executing various types of applications including (but not limited to) video game programs. CPU 204 executes a boot program stored, for example, in a boot ROM to initialize game console 100 and then executes an application (or applications) stored on optical disc 104, which is inserted in optical disk drive 208. User-accessible eject button 210 provided on housing 110 of game console 100 may be used to eject an optical disk from disk drive 208.

In one example implementation, optical disk drive 208 receives both optical disks of a first type (e.g., of a first size and/or of a first data structure, etc.) containing applications developed to take advantage of the capabilities of CPU 204 and graphics processor 216 and optical disks of a second type (e.g., of a second size and/or a second data structure) containing applications originally developed for execution by a CPU and/or graphics processor having capabilities different than those of CPU 204 and/or graphics processor 216. For example, the optical disks of the second type may be applications originally developed for the Nintendo GameCube platform.

CPU 204 is connected to system LSI 202 that includes graphics processing unit (GPU) 216 with an associated graphics memory 220, audio digital signal processor (DSP) 218, internal main memory 222 and input/output (IO) processor 224.

IO processor 224 of system LSI 202 is connected to one or more USB ports 226, one or more standard memory card slots (connectors) 228, WiFi module 230, flash memory 232 and wireless controller module 240.

USB ports 226 are used to connect a wide variety of external devices to game console 100. These devices include by way of example without limitation game controllers, keyboards, storage devices such as external hard-disk drives, printers, digital cameras, and the like. USB ports 226 may also be used for wired network (e.g., LAN) connections. In one example implementation, two USB ports 226 are provided.

Standard memory card slots (connectors) 228 are adapted to receive industry-standard-type memory cards (e.g., SD memory cards). In one example implementation, one memory card slot 228 is provided. These memory cards are generally used as data carriers but of course this use is provided by way of illustration, not limitation. For example, a player may store game data for a particular game on a memory card and bring the memory card to a friend's house to play the game on the friend's game console. The memory cards may also be used to transfer data between the game console and personal computers, digital cameras, and the like.

WiFi module 230 enables game console 100 to be connected to a wireless access point. The access point may provide internet connectivity for on-line gaming with players at other locations (with or without voice chat capabilities), as well as web browsing, e-mail, file downloads (including game downloads) and many other types of on-line activities. In some implementations, WiFi module 230 may also be used for communication with other game devices such as suitably-equipped hand-held game devices. Module 230 is referred to herein as “WiFi”, which is generally a designation used in connection with the family of IEEE 802.11 specifications. However, game console 100 may of course alternatively or additionally use wireless modules that conform to other wireless standards.

Flash memory 232 stores, by way of example without limitation, game save data, system files, internal applications for the console and downloaded data (such as games).

Wireless controller module 240 receives signals wirelessly transmitted from one or more controllers 107 and provides these received signals to IO processor 224. The signals transmitted by controller 107 to wireless controller module 240 may include signals generated by controller 107 itself as well as by other devices that may be connected to controller 107. By way of example, some games may utilize separate right- and left-hand inputs. For such games, another controller (not shown) may be connected (e.g., by a wired connection) to controller 107 and controller 107 can transmit to wireless controller module 240 signals generated by itself and by the other controller.

Wireless controller module 240 may also wirelessly transmit signals to controller 107. By way of example without limitation, controller 107 (and/or another game controller connected thereto) may be provided with vibration circuitry and vibration circuitry control signals may be sent via wireless controller module 240 to control the vibration circuitry (e.g., by turning the vibration circuitry on and off). By way of further example without limitation, controller 107 may be provided with (or be connected to) a speaker (not shown) and audio signals for output from this speaker may be wirelessly communicated to controller 107 via wireless controller module 240. By way of still further example without limitation, controller 107 may be provided with (or be connected to) a display device (not shown) and display signals for output from this display device may be wirelessly communicated to controller 107 via wireless controller module 240.

Proprietary memory card slots 246 are adapted to receive proprietary memory cards. In one example implementation, two such slots are provided. These proprietary memory cards have some non-standard feature(s) such as a non-standard connector and/or a non-standard memory architecture. For example, one or more of the memory card slots 246 may be adapted to receive memory cards used with the Nintendo GameCube platform. In this case, memory cards inserted in such slots can transfer data from games developed for the GameCube platform. In an example implementation, memory card slots 246 may be used for read-only access to the memory cards inserted therein and limitations may be placed on whether data on these memory cards can be copied or transferred to other storage media such as standard memory cards inserted into slots 228.

One or more controller connectors 244 are adapted for wired connection to respective game controllers. In one example implementation, four such connectors are provided for wired connection to game controllers for the Nintendo GameCube platform. Alternatively, respective wireless receivers may be connected to connectors 244 to receive signals from wireless game controllers. These connectors enable players, among other things, to use controllers for the Nintendo GameCube platform when an optical disk for a game developed for this platform is inserted into optical disk drive 208.

A connector 248 is provided for connecting game console 100 to DC power derived, for example, from an ordinary wall outlet. Of course, the power may be derived from one or more batteries.

GPU 216 performs image processing based on instructions from CPU 204. GPU 216 includes, for example, circuitry for performing calculations necessary for displaying three-dimensional (3D) graphics. GPU 216 performs image processing using graphics memory 220 dedicated for image processing and a part of internal main memory 222. GPU 216 generates image data for output to television 102 by audio/video connector 214 via audio/video IC (interface) 212.

Audio DSP 218 performs audio processing based on instructions from CPU 204. The audio generated by audio DSP 218 is output to television 102 by audio/video connector 214 via audio/video IC 212.

External main memory 206 and internal main memory 222 are storage areas directly accessible by CPU 204. For example, these memories can store an application program such as a game program read from optical disc 104 by the CPU 204, various types of data or the like.

ROM/RTC 238 includes a real-time clock and preferably runs off of an internal battery (not shown) so as to be usable even if no external power is supplied. ROM/RTC 238 also may include a boot ROM and SRAM usable by the console.

Power button 242 is used to power game console 100 on and off. In one example implementation, power button 242 must be depressed for a specified time (e.g., one or two seconds) to turn the console off so as to reduce the possibility of inadvertently turn-off. Reset button 244 is used to reset (re-boot) game console 100.

With reference to FIGS. 3 and 4, example controller 107 includes a housing 301 on which operating controls 302 a-302 h are provided. Housing 301 has a generally parallelepiped shape and is sized to be conveniently grasped by a player's hand. Cross-switch 302 a is provided at the center of a forward part of a top surface of the housing 301. Cross-switch 302 a is a cross-shaped four-direction push switch which includes operation portions corresponding to the directions designated by the arrows (front, rear, right and left), which are respectively located on cross-shaped projecting portions. A player selects one of the front, rear, right and left directions by pressing one of the operation portions of the cross-switch 302 a. By actuating cross-switch 302 a, the player can, for example, move a character in different directions in a virtual game world.

Cross-switch 302 a is described by way of example and other types of operation sections may be used. By way of example without limitation, a composite switch including a push switch with a ring-shaped four-direction operation section and a center switch may be used. By way of further example without limitation, an inclinable stick projecting from the top surface of housing 301 that outputs signals in accordance with the inclining direction of the stick may be used. By way of still further example without limitation, a horizontally slidable disc-shaped member that outputs signals in accordance with the sliding direction of the disc-shaped member may be used. By way of still further example without limitation, a touch pad may be used. By way of still further example without limitation, separate switches corresponding to at least four directions (e.g., front, rear, right and left) that output respective signals when pressed by a player can be used.

Buttons (or keys) 302 b through 302 g are provided rearward of cross-switch 302 a on the top surface of housing 301. Buttons 302 b through 302 g are operation devices that output respective signals when a player presses them. For example, buttons 302 b through 302 d are respectively an “X” button, a “Y” button and a “B” button and buttons 302 e through 302 g are respectively a select switch, a menu switch and a start switch, for example. Generally, buttons 302 b through 302 g are assigned various functions in accordance with the application being executed by game console 100. In an exemplary arrangement shown in FIG. 3A, buttons 302 b through 302 d are linearly arranged along a front-to-back centerline of the top surface of housing 301. Buttons 302 e through 302 g are linearly arranged along a left-to-right line between buttons 302 b and 302 d. Button 302 f may be recessed from a top surface of housing 701 to reduce the possibility of inadvertent pressing by a player grasping controller 107.

Button 302 h is provided forward of cross-switch 302 a on the top surface of the housing 301. Button 302 h is a power switch for remote on-off switching of the power to game console 100. Button 302 h may also be recessed from a top surface of housing 301 to reduce the possibility of inadvertent pressing by a player.

A plurality (e.g., four) of LEDs 304 is provided rearward of button 302 c on the top surface of housing 301. Controller 107 is assigned a controller type (number) so as to be distinguishable from other controllers used with game console 100 and LEDs 304 may be used to provide a player a visual indication of this assigned controller number. For example, when controller 107 transmits signals to wireless controller module 240, one of the plurality of LEDs corresponding to the controller type is lit up.

With reference to FIG. 3B, a recessed portion 308 is formed on a bottom surface of housing 301. Recessed portion 308 is positioned so as to receive an index finger or middle finger of a player holding controller 107. A button 302 i is provided on a rear, sloped surface 308 a of the recessed portion. Button 302 i functions, for example, as an “A” button which can be used, by way of illustration, as a trigger switch in a shooting game.

As shown in FIG. 4, an imaging element 305 a is provided on a front surface of controller housing 301. Imaging element 305 a is part of the imaging information calculation section of controller 107 that analyzes image data received from markers 108 a and 108 b. Imaging information calculation section 305 has a maximum sampling period of, for example, about 200 frames/sec., and therefore can trace and analyze even relatively fast motion of controller 107. Additional details of the operation of this section may be found in Application Nos. 60/716,937, entitled “VIDEO GAME SYSTEM WITH WIRELESS MODULAR HANDHELD CONTROLLER,” filed on Sep. 15, 2005 (corresponding to U.S. Patent Publication No. 2007-0066394 A1); 60/732,648, entitled “INFORMATION PROCESSING PROGRAM,” filed on. Nov. 3, 2005 (corresponding to U.S. Patent Publication No. 2007-0072674 A1); and application No. 60/732,649, entitled “INFORMATION PROCESSING SYSTEM AND PROGRAM THEREFOR,” filed on Nov. 3, 2005 (corresponding to U.S. Patent Publication No. 2007-0060228 A1). The entire contents of each of these applications are expressly incorporated herein.

Connector 303 is provided on a rear surface of controller housing 301. Connector 303 is used to connect devices to controller 107. For example, a second controller of similar or different configuration may be connected to controller 107 via connector 303 in order to allow a player to play games using game control inputs from both hands. Other devices including game controllers for other game consoles, input devices such as keyboards, keypads and touchpads and output devices such as speakers and displays may be connected to controller 107 using connector 303.

For ease of explanation in what follows, a coordinate system for controller 107 will be defined. As shown in FIGS. 3 and 4, a left-handed X, Y, Z coordinate system has been defined for controller 107. Of course, this coordinate system is described by way of example without limitation and the systems and methods described herein are equally applicable when other coordinate systems are used.

As shown in the block diagram of FIG. 5A, controller 107 includes a three-axis, linear acceleration sensor 507 that detects linear acceleration in three directions, i.e., the up/down direction (Z-axis shown in FIGS. 3 and 4), the left/right direction (X-axis shown in FIGS. 3 and 4), and the forward/backward direction (Y-axis shown in FIGS. 3 and 4). Alternatively, a two-axis linear accelerometer that only detects linear acceleration along each of the Y-axis and Z-axis, for example, may be used or a one-axis linear accelerometer that only detects linear acceleration along the Z-axis, for example, may be used. Generally speaking, the accelerometer arrangement (e.g., three-axis or two-axis) will depend on the type of control signals desired. As a non-limiting example, the three-axis or two-axis linear accelerometer may be of the type available from Analog Devices, Inc. or STMicroelectronics N.V. Preferably, acceleration sensor 507 is an electrostatic capacitance or capacitance-coupling type that is based on silicon micro-machined MEMS (micro-electromechanical systems) technology. However, any other suitable accelerometer technology (e.g., piezoelectric type or piezoresistance type) now existing or later developed may be used to provide three-axis or two-axis linear acceleration sensor 507.

As one skilled in the art understands, linear accelerometers, as used in acceleration sensor 507, are only capable of detecting acceleration along a straight line corresponding to each axis of the acceleration sensor. In other words, the direct output of acceleration sensor 507 is limited to signals indicative of linear acceleration (static or dynamic) along each of the two or three axes thereof. As a result, acceleration sensor 507 cannot directly detect movement along a non-linear (e.g. arcuate) path, rotation, rotational movement, angular displacement, tilt, position, attitude or any other physical characteristic.

However, through additional processing of the linear acceleration signals output from acceleration sensor 507, additional information relating to controller 107 can be inferred or calculated (i.e., determined), as one skilled in the art will readily understand from the description herein. For example, by detecting static, linear acceleration (i.e., gravity), the linear acceleration output of acceleration sensor 507 can be used to determine tilt of the object relative to the gravity vector by correlating tilt angles with detected linear acceleration. In this way, acceleration sensor 507 can be used in combination with micro-computer 502 of controller 107 (or another processor) to determine tilt, attitude or position of controller 107. Similarly, various movements and/or positions of controller 107 can be calculated through processing of the linear acceleration signals generated by acceleration sensor 507 when controller 107 containing acceleration sensor 507 is subjected to dynamic accelerations by, for example, the hand of a user.

In another embodiment, acceleration sensor 507 may include an embedded signal processor or other type of dedicated processor for performing any desired processing of the acceleration signals output from the accelerometers therein prior to outputting signals to micro-computer 502. For example, the embedded or dedicated processor could convert the detected acceleration signal to a corresponding tilt angle (or other desired parameter) when the acceleration sensor is intended to detect static acceleration (i.e., gravity).

Other types of devices usable to detect or determine movement and/or orientation such as gyroscopes may be used in addition to or as an alternative to the acceleration sensors. By way of example and without limitation, a gyroscope may be used to refine or correct the measurements or readings from an accelerometer.

Returning to FIG. 5A, imaging information calculation section 505 of controller 107 includes infrared filter 528, lens 529, imaging element 305 a and image processing circuit 530. Infrared filter 528 allows only infrared light to pass therethrough from the light that is incident on the front surface of controller 107. Lens 529 collects and focuses the infrared light from infrared filter 528 on imaging element 305 a. Imaging element 305 a is a solid-state imaging device such as, for example, a CMOS sensor or a CCD. Imaging element 305 a captures images of the infrared light from markers 108 a and 108 b collected by lens 529. Accordingly, imaging element 305 a captures images of only the infrared light that has passed through infrared filter 528 and generates image data based thereon. This image data is processed by image processing circuit 530 which detects an area thereof having high brightness, and, based on this detecting, outputs processing result data representing the detected coordinate position and size of the area to communication section 506. From this information, the direction in which controller 107 is pointing and the distance of controller 107 from display 101 can be determined.

FIG. 5B shows sensors 108 a, 108 b positioned below the display screen 101 of the television 102. As shown in FIG. 5B, when controller 107 is pointing toward the sensors, it is not actually pointing at the center of display screen 101. However, the game program or application executed by game machine 100 may treat this situation as one in which controller 107 is pointed at the center of the screen. In this case, the actual coordinates and the program coordinates will differ, but when the user is sufficiently far from the television, his or her brain automatically corrects for the difference between the coordinates seen by the eye and the coordinates for hand movement.

Again returning to FIG. 5A, vibration circuit 512 may also be included in controller 107. Vibration circuit 512 may be, for example, a vibration motor or a solenoid. Controller 107 is vibrated by actuation of the vibration circuit 512 (e.g., in response to signals from game console 100), and the vibration is conveyed to the hand of the player grasping controller 107. Thus, a so-called vibration-responsive game may be realized.

As described above, acceleration sensor 507 detects and outputs the acceleration in the form of components of three axial directions of controller 107, i.e., the components of the up-down direction (Z-axis direction), the left-right direction (X-axis direction), and the front-rear direction (the Y-axis direction) of controller 107. Data representing the acceleration as the components of the three axial directions detected by acceleration sensor 507 is output to communication section 506. Based on the acceleration data which is output from acceleration sensor 507, a motion of controller 107 can be determined.

Communication section 506 includes micro-computer 502, memory 503, wireless module 504 and antenna 505. Micro-computer 502 controls wireless module 504 for transmitting and receiving data while using memory 503 as a storage area during processing. Micro-computer 502 is supplied with data including operation signals (e.g., cross-switch, button or key data) from operation section 302, acceleration signals in the three axial directions (X-axis, Y-axis and Z-axis direction acceleration data) from acceleration sensor 507, and processing result data from imaging information calculation section 505. Micro-computer 502 temporarily stores the data supplied thereto in memory 503 as transmission data for transmission to game console 100. The wireless transmission from communication section 506 to game console 100 is performed at predetermined time intervals. Because game processing is generally performed at a cycle of 1/60 sec. (16.7 ms), the wireless transmission is preferably performed at a cycle of a shorter time period. For example, a communication section structured using Bluetooth (registered trademark) technology can have a cycle of 5 ms. At the transmission time, micro-computer 502 outputs the transmission data stored in memory 503 as a series of operation information to wireless module 504. Wireless module 504 uses, for example, Bluetooth (registered trademark) technology to send the operation information from antenna 505 as a carrier wave signal having a specified frequency. Thus, operation signal data from operation section 302, the X-axis, Y-axis and Z-axis direction acceleration data from acceleration sensor 507, and the processing result data from imaging information calculation section 505 are transmitted from controller 107. Game console 100 receives the carrier wave signal and demodulates or decodes the carrier wave signal to obtain the operation information (e.g., the operation signal data, the X-axis, Y-axis and Z-axis direction acceleration data, and the processing result data). Based on this received data and the application currently being executed, CPU 204 of game console 100 performs application processing. If communication section 506 is structured using Bluetooth (registered trademark) technology, controller 107 can also receive data wirelessly transmitted thereto from devices including game console 100.

In one example embodiment, normalization of the accelerometer outputs is performed to account for, among other things, differences in sensitivity that may exist between accelerometers in different controllers and for differences in sensitivity that may exist among the different axes of the same accelerometer.

The systems and methods described herein involve generating a normalization factor for normalizing accelerometer outputs. At or near the beginning of a game, for example, the acceleration vectors for each axis of the accelerometer are monitored for a specified time period (e.g., 20 frames or about 0.3 seconds). If, for this time period, the largest difference in the acceleration vectors for each axis is within some specified limit, the average of the acceleration vectors for each axis over the time period is computed. The inverse of the magnitude of the average vector for each axis is calculated and is used as a normalization constant for that axis. Subsequent readings for the acceleration vectors are multiplied with this normalization constant. Thus, for example, if an accelerometer axis aligned with gravity obtained an average reading of 0.8 g, the inverse of this average (i.e. 1.25) would be the normalization constant and accelerometer readings for this axis would be multiplied by 1.25.

In the above normalization method, only the magnitude of the average acceleration vector is considered, not the direction. Moreover, a scale factor is calculated for each accelerometer of the controller device, hence there is one, for example, for the accelerometer of controller 107 and one for any accelerometer contained in any other controller connected (either wirelessly or by wire) to controller 107. Because signals from controller 107 and any controller connected thereto are contained in different data fields of communications to game console 100, the console can determine which normalized accelerations come from controller 107 and which come from any controller connected to controller 107.

In one exemplary embodiment, the normalization factor for the accelerometer is calculated at the start of the game, when the player is getting ready to play. However, the embodiment is not limited to this choice of time frame, and the calculation may occur at any time period, as it happens during re-calibration, described hereinafter.

The normalization occurs without the user knowing about it. This eliminates a number of tedious screens that the user may have to process, and also eliminates the chance of user error if the user were required to perform the normalization.

In yet another exemplary embodiment, even if the normalization factor is calculated before the game play actually begins during an initial set-up, there may be need for (re)calibration since the scale factor may change during a game play session. Even though the scale factor should not change in theory with respect to one controller 107 in a given user session, the orientation of controller 107 may affect the readings. More specifically, the X-axis may be a little more sensitive than the Y-axis, for instance, so if controller 107 were to rotate in one direction or another, the system would get slightly different sensitivity values based on that. This might occur, for example, during a game play session by a particular player, when the player changes the way he/she plays slightly. If, for example, he/she rotates the controller so that the gravity is acting on a different axis of the accelerometer, this axis may actually have slightly different sensitivity values than the other axes, which would produce a slightly different scale factor as well. Thus, the calibration value may change over the course of the game, and the normalization process is repeated at predetermined time periods.

The above described normalization method looks for a time period of relative rest for the controller. However, if the player wildly shakes the controller for the entire time, then a default normalization value of, for example, 1.0 is used.

FIG. 6 shows a flowchart of an exemplary illustrative non-limiting process performed by the video game console 100 calibrating the readings of an accelerometer of controller 107 during a game play session. In the example shown, in step 302, an initialization of controller 107 occurs and a default normalization value, e.g., 1.0 is set, wherein game console 100 asks the user to point controller 107 at the center of the display screen 101 to establish the center point between markers 108 a and 108 b. Subsequently, in step 304, console 100 determines if normalization of the accelerometer has occurred. If the answer is negative, then the normalization process A (shown in FIG. 7) is performed. On the other hand, if the answer is positive, then play continues in step 306.

In step 308, game console 100 determines if a certain amount of time has passed in the course of the play. This amount of time is related to the periodic re-calibration performed for the accelerometer(s) of the controller(s). If the predetermined amount of time has not passed, then the process goes back to step 306. However, if the answer in step 308 is positive, then the system performs the normalization A in step 310. Finally, in step 312, the system determines if the play has ended. If not, then the process goes back to step 306 and play continues. If however, the game has ended, then the process ends.

FIG. 7 shows a flowchart of an exemplary illustrative non-limiting normalization process A. In step 402, a predetermined a time period is considered, for example, 0.3 sec. Subsequently, in step 404, the game console 100 looks for the values of the acceleration vectors in each axis for the accelerometer sensor for a predetermined number of frames (e.g., 20 frames) in the predetermined amount of time. Then, game console 100 determines whether the largest difference for the accelerations vectors for each axis for each frame is within a predetermined small value (step 406). This would indicate that the controller is held relatively idly. If the answer in step 406 is negative, then the default value, for example, of 1.0 is used as the normalization factor, and the normalization continues to step 416.

If the answer in step 406 is positive, then the average of all acceleration vectors over the time period is calculated in step 410, followed by the calculation of the magnitude of the average acceleration vector for each axis in step 412. The normalization process continues by calculating the inverse of the magnitude of the average vector found in step 412 to yield the normalization factor (step 414). Finally, the game console 100 normalizes each reading for the acceleration vectors by multiplying with the normalization factor found in step 414 (step 416).

In another example implementation, game console 100 may prompt a user to hold controller 107 so that a particular accelerometer axis is aligned with gravity. The average acceleration vector for that particular axis over a predetermined period of time may be calculated to provide the normalization factor. In another example implementation, game console 100 may prompt a user to hold controller 107 so that each accelerometer axis is sequentially aligned with gravity. The average acceleration vector for each axis over a predetermined period of time may be calculated to provide the respective normalization factors.

The systems and methods described herein may be implemented in hardware, firmware, software and combinations thereof. Software or firmware may be executed by a general-purpose or specific-purpose computing device including a processing system such as a microprocessor and a microcontroller. The software may, for example, be stored on a storage medium (optical, magnetic, semiconductor or combinations thereof) and loaded into a RAM for execution by the processing system. The systems and methods described herein may also be implemented in part or whole by hardware such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), logic circuits and the like.

While the systems and methods have been described in connection with what is presently considered to practical and preferred embodiments, it is to be understood that these systems and methods are not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. 

1. A method for calibrating the operation of the acceleration sensor of a remote controller used in conjunction with a video game console so that it yields consistent readings, comprising: considering a predetermined time period after initialization of the controller; considering the values of the acceleration vectors of the acceleration sensor along each of a plurality of orthogonal axes, for a predetermined number of video frames over the predetermined time period; determining whether the largest difference in the acceleration vectors for each frame over the predetermined time period is smaller than a predetermined limit; setting a normalization factor based on said determining; multiplying each acceleration vector for each axis of the acceleration sensor with said normalization factor.
 2. The method according to claim 1, wherein if the result of said determining is positive, then the normalization factor is equal to the inverse of the magnitude of the average acceleration vector over said predetermined time period for each axis.
 3. The method according to claim 1, wherein if the result of said determining is negative, then the normalization factor is equal to a predetermined value.
 4. The method according to claim 1, wherein said method is repeated periodically during the duration of a play session of the game video console.
 5. A system for calibrating the readings of the accelerometer sensor of a remote controller used in conjunction with a video game console so that it yields consistent readings, comprising a remote controller sending and receiving data from the video game console, wherein said remote controller comprises an accelerometer sensor yielding values for the acceleration vectors along each of a plurality of orthogonal axes; time period consideration programmed logic circuitry in said video game console, for considering a predetermined time period after initialization of said remote controller; acceleration values consideration programmed logic circuitry for considering the values of the acceleration vectors of the acceleration sensor along each axis, for a predetermined number of video frames over said predetermined time period; threshold determination programmed logic circuitry for determining whether the largest difference in the acceleration vectors for each frame over the predetermined time period is smaller than a predetermined limit; setting programmed logic circuitry for setting a normalization factor based on the result of said threshold determination programmed logic circuitry; and normalization programmed logic circuitry for multiplying each acceleration vector for each axis of the acceleration sensor with said normalization factor.
 6. The system according to claim 5, wherein if the result of said threshold determination programmed logic circuitry is positive, then the normalization factor is equal to the inverse of the magnitude of the average acceleration vector over said predetermined time period for each axis.
 7. The system according to claim 5, wherein if the result of said threshold determination programmed logic circuitry is negative, then the normalization factor is equal to a predetermined value.
 8. The system according to claim 5, wherein the calibration of the readings of the accelerometer sensor of the remote controller is repeated periodically during the duration of a play session of the game video console. 